Knowledge Corner

Preliminary Sizing of Concrete Beams

Member Span/Depth Ratio Max. Recommended Span
Rectangular Beam 10 to 14 (cont. 20 to 26) 8m (cont. 12m)
Flanged Beam 12 to 18 (cont. 18 to 21) 10m (cont. 14m)
Cantilever 2 to 6 5m
Band Beams 18 to 20 12m

The maximum spans listed here are not absolute limits. Longer spans are possible with every type, but
may not be economical. As a rule of thumb for estimates of thickness above the span on deflection ratio’s
should be multiplied by “maximum recommended span”/”actual span”)
The higher number are given for light loadings (about 1.5 kpa) and the lower numbers for heavy loadings
(about 10kpa)
*2010 Design Tips by Rowing Engineer



Preliminary Sizing of Concrete Slabs

Member Span/Depth Ratio Max. Recommended Span
One-way Simply Supported 20 to 30 6m
One-way Continuous 28 to 34 7m
Two-way Simply Supported 24 to 34 6.5m
Two-way Countinuous 30 to 34 7.5m
Cantilever 6 to 11 3m
Flat Slab 23 to 28 7m

The maximum spans listed here are not absolute limits. Longer spans are possible with every type, but
may not be economical. As a rule of thumb for estimates of thickness above the span on deflection ratio’s
should be multiplied by “maximum recommended span”/”actual span”)
The higher number are given for light loadings (about 1.5 kpa) and the lower numbers for heavy loadings
(about 10kpa)
*2010 Design Tips by Rowing Engineer



Preliminary Sizing of Steel Members

Element Span/depth ratio Maximum span
Purlins 32 12m
Roof beams (light dead loading) 18-30 6-30m
Floor I beams and joists 18 18m
Floor Plate girder 41194 25m (80’)
Floor Joist (steel only) 17 6-9m (20-30’)
Castellated UB’s* 14-17 12-20m(40-70’)
Transfer beams 10 6-30m
Trusses supporting floors 10 6-30m
Roof trusses (pitch>20) 14-15 17m (55’)
Space Frames 15-30 100m (300’)
Primary beams (supported by columns) 41197 12m (40’)
Secondary beams (supported by other beams) 15-25 10m (33’)
Portal frame leg 35-40 60m (200’)
Simple span rafter 24 30m (100’)
Simple span roof beam 15 25m (80’)
Con’t beam or joist .85 * simple span value
Column SHS H/D 20-35 2-8m

*2010 Design Tips by Rowing Engineer


Engineering Related Quotes

These quotes are provided to inspire you, give you confidence and show you that engineering has no black
and white, just shades of grey.

“The road to success is always under construction”
Get it right….CIVIL ENGINEERS

A common mistake that people make when trying to design something completely foolproof is to underestimate the ingenuity of complete fools.
- Douglas Adams

Aeroplanes are not designed by science, but by art in spite of some pretence and humbug to the contrary. I do not mean to suggest that engineering can do without science, on the contrary, it stands on scientific foundations, but there is a big gap between scientific research and the engineering product which has to be bridged by the art of the engineer.
- British Engineer to the Royal Aeronautical Society, 1922.

A good scientist is a person with original ideas. A good engineer is a person who makes a design that works with as few original ideas as possible
- Freeman Dyson
Read More..



Great Engineers

Engineers have always made a difference. They are the thinkers and innovators that shape our world. Find out here about some of the greatest engineers of all time.

Ove Arup (1895 - 1988)
Sir Ove Nyquist Arup is generally considered one of the foremost engineers of the twentieth century. Groundbreaking use of precast concrete, structural glue and computer analysis helped to make Arup's reputation, and that of his firm, Arup. The multi-disciplinary company provided engineering, architectural, and other services for the built environment.
Notible projects included the The Sydney Opera House, which Arup worked on from 1957 to 1973. Before his death Arup received a Knighthood from both the British and Danish monarchy along with a plethora of industry commendations.

Sir John Fleetwood Baker (1901-1985)
Sir John Fleetwood Baker was one of the first winners of the Institution's Gold Medal award. During the 1930’s Baker carried out tests on buildings which brought a revelation that led to Baker’s life work on the development of the plastic theory of design.
During the Second World War, Baker was appointed Scientific Adviser to the Ministry of Home Security, focussing on reducing the impact of bombing of buildings, especially industrial sites and factories. Read More..